noun an interval of geologicaltime, the subdivision of an era and itself divided into epochs

The time taken for a single cycle of some regular event, such as a complete sequence of the light curve of a variable star, a single journey of an object around its orbit, or between two pulses from a pulsar

An interval of time during which one or more phenomena, conditions, or events occur. For example, a busy period, or an early-failure period.

The interval of time that elapses between two consecutive events of a periodically repeated phenomenon. For instance, the duration of a complete cycle. Also, the time interval elapsing between successive occurrences of the same phases of a cyclic event. Its symbol is T.

A series of elements which form a horizontal row within a periodic table of chemical elements.